The recognition of two externally distinct morphological forms of finless porpoises as separate biological species (Neophocaena phocaenoides and N. asiaeorientalis) was accepted recently when it was demonstrated that the two forms are reproductively isolated (and likely have been separated since the last glacial maximum) even though they occur sympatrically in a fairly large area of eastern Asia (Wang et al. 2008). Differences in the external morphology of the dorsal aspect of the two species are distinguishable even amongst free-ranging animals (Wang et al. 2010). Intermediates between the two main forms have never been reported even though several hundreds to thousands of carcasses have been examined. The two species also clearly differ in craniometry (Amano et al. 1992, Jefferson 2002). There is evidence to suggest subpopulation structure within N. phocaenoides in some areas (Jefferson 2002) and this may apply throughout much of the species’ wide distribution.

Justification:
There is no population estimate for Indo-Pacific Finless Porpoises throughout their wide range, which appears to be discontinuous (Pilleri and Gihr 1975, Reeves et al. 1997). They are regularly sighted in some areas.

Partly because of their small size, phocoenids are exceptionally vulnerable to incidental mortality in gillnets (e.g., Jefferson and Curry 1994). Neophocaena phocaenoides is smaller than N. asiaeorientalis (thus, if anything, probably even less able to break free once entangled in a net) and incidental mortality in fishing gear has been documented throughout its range. Fishing effort with gear documented to catch Finless Porpoises (including gillnets, trawls, stow nets and seines) is intense in many areas where the species occurs or occurred. With some of the largest concentrations of humans in the world living along the shores of and harvesting the resources from the warm coastal waters inhabited by Indo-Pacific Finless Porpoises, the impacts of human activities on this species must be considerable. Although not quantified rigorously as for some N. asiaeorientalis populations, regional declines (and possible local extirpations) of N. phocaenoides have been reported, presumably due to fishing pressure, coastal development and industrialization, pollution and heavy vessel traffic (see Reeves et al. 1997, Collins et al. 2005, Braulik et al. 2010).

Although the data are far from sufficient to make a rigorous quantitative assessment of population trend for this species throughout its range, the scale of threats is large enough over enough of the range to suspect and infer a decline of at least 30% over the last three generations (about 50 years, see Taylor et al. 2007). The factor most responsible for such a decline would be incidental mortality in fisheries, but the loss and degradation of habitat are likely contributing factors as well. None of the threats has been seriously addressed in any part of the species’ range, even though threat levels are likely increasing.

Therefore, as is true of the other species of Finless Porpoise (N. asiaeorientalis), the Indo-Pacific species qualifies for Vulnerable A2cde, considering that the causes of the suspected/inferred decline in population size—bycatch (interpreted here as “exploitation”), decline in habitat quality, and possibly pollution—have not ceased and are not well understood.

The type specimen is supposed to have come from the Cape of Good Hope, but this location is believed to be erroneous; it is now generally accepted that the type locality is the Malabar coast of India (Rice 1998, Jefferson and Hung 2004).

In general, Indo-Pacific Finless Porpoises occur in a narrow strip of shallow (usually <50 m deep) coastal marine waters (as well as some river mouths and estuaries) around the northern rim of the Indian and western Pacific Oceans from the Arabian (Persian) Gulf (Preen 2004, Collins et al. 2005) eastwards around the rim of the Indian Ocean to the Indo-Malay region and to Java, Indonesia (but apparently not the Philippines) and northwards to the Taiwan Strait and central Chinese waters (Gao 1991, Gao and Zhou 1995). This is the more tropical and wide-ranging of the two currently recognized species of finless porpoises. A record of the species from northern Chinese waters (Wang 1992) probably represents a rare or extralimital event. Finless porpoises are seen regularly (when sea conditions are favourable) in Sarawak, East Malaysia (Minton et al. 2011), in at least parts of Peninsular Malaysia (e.g. they are the most frequently seen cetaceans in Langkawi according to Louisa Ponnampalam, Reeves pers. comm. 2011), at least seasonally in Hong Kong (Jefferson et al. 2002a), and in parts of the western Taiwan Strait (Wang unpublished data). They are also present along the East Kalimantan coastline of Borneo (D. Kreb pers. comm. 2011).

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states. States within the hypothetical range but for which no confirmed records exist are included in the Presence Uncertain list.

Finless porpoises are small and cryptic and therefore difficult to survey. Estimates of abundance have been made for only a few areas (Jefferson and Hung 2004, IWC 2006) but mostly in regions where the Narrow-ridged species (N. asiaeorientalis) dominates, if not exists solely.

Numbers of Indo-Pacific Finless Porpoises in Hong Kong and adjacent waters were estimated to be at least 217 (CV= 21-150%) (Jefferson et al. 2002a). An estimate for the coastal waters of Bangladesh was 1,382 (CV=55%) but the density was very low compared to reported densities of Narrow-ridged Finless Porpoises in Japanese waters (Smith et al. 2008).

Indo-Pacific Finless Porpoises are found mainly in coastal waters, including shallow bays, mangrove swamps, and estuaries. They can also occur quite far from shore (up to 240 km) in waters < 200 m deep. It is uncertain which of the two currently recognized species of Finless Porpoises (possibly both) occurs farther offshore, especially in areas of sympatry.

Indo-Pacific Finless Porpoises appear to have a strong preference for waters with a sandy or soft bottom (Jefferson and Hung 2004).

Small fishes, cephalopods, and crustaceans (mainly demersal species) form the diet of Finless Porpoises (see Jefferson and Hung 2004).

Finless Porpoises, like other phocoenids (Jefferson and Curry 1994), are extremely susceptible to entanglement in gillnets, and large numbers have been, and continue to be, killed in many parts of their range (Jefferson et al. 2002b). Finless Porpoises are caught in nets in Iranian, Indian, Pakistani and Malaysian coastal waters, although there are no good estimates of the magnitude of such catches (e.g., see Collins et al. 2005, Jaaman et al. 2009, Braulik et al. 2010). In East Malaysia, Finless Porpoises are caught as bycatch in ‘fish stakes’ in Sabah (Jaaman et al. 2009) and one individual was found entangled in the line of a crab trap in Sarawak (G. Minton pers. comm. 2011). Yang et al. (1999) reported that Finless Porpoises were the most frequently captured cetaceans in fishing gear along the Chinese coast and estimated that more than 2,000 were taken in 1994, mainly in trawl, gill, and stow nets. In the waters of western Taiwan (where the two species of Finless Porpoises are sympatric), a considerable number of both species are taken in trammel nets, trawl nets, stow nets, and other gear (Wang unpublished data). In Hong Kong waters, porpoises are caught regularly by trawl nets and gillnets, but there are no estimates of bycatch levels (Parsons and Jefferson 2000, Jefferson et al. 2002b). Given the numbers and types of net fisheries in Chinese coastal waters, the apparently high bycatch of Finless Porpoises (e.g. Zhou and Wang 1994, Yang et al. 1999) is a serious concern. No large-scale direct hunting of this species is known to occur. In some parts of their range, people apparently are averse to eating finless porpoises (Kasuya 1999, Wang unpublished data) but in other areas they are consumed.

As a coastal species, the Indo-Pacific Finless Porpoise is also affected by habitat loss and degradation, boat traffic, and pollution. The extensive modification of coastlines for shrimp farming, causeways and harbour (and other) development throughout Asia (including the Arabian Gulf) means that there is less habitat for Finless Porpoises (Reeves et al. 2003, Braulik et al. 2010). Although pathology related to contaminant exposure has not been reported in Finless Porpoises, pollution is considered a potentially serious threat (Kasuya 1999, Iwata et al. 1994, Parsons and Chan 1998, Minh et al. 1999, Parsons 1999, Jefferson et al. 2002b, Ramu et al. 2005). The number of reported small cetacean strandings in Hong Kong has increased in recent years, partly due to increasing public awareness of local cetaceans, but also possibly due to escalating levels of human disturbance and pollution (T.A. Jefferson pers. comm. 2007). In the Arabian Gulf and Gulf of Oman/Sea of Oman, chemicals from recent wars exacerbate total pollution loads in coastal waters from the usual sources such as industry, agriculture and households (Braulik et al. 2010). Vessel collisions, especially involving high-speed ferries, may be a particular problem for porpoises in Hong Kong (Parsons and Jefferson 2000).

The following summary of examples illustrates the problems faced by this species:

In Chinese waters (excluding the considerable fisheries operating in Taiwanese waters), more than 3.5 million gillnets were estimated to be in use in the early 1990s (Zhou and Wang 1994). In India, the use of gillnets reportedly had increased from about 18,000 in 1950 to more than 216,000 by 1980 and gillnets were also being used extensively in Sri Lanka, Bangladesh and Myanmar (Mohan 1994). Since the time of those reports, gillnetting effort certainly would have increased considerably in these and other regions because there are few (if any) restrictions on this kind of fishing gear anywhere in the range of the species. Porpoise habitat in Myanmar is heavily fished with gillnets and other types of gear capable of taking small cetaceans incidentally (Smith and Than Tun 2008). A drift gillnet fishery for elasmobranchs is of concern in the Bangladesh Sundarbans (Smith et al. 2008). In East Malaysia, Finless Porpoise numbers are thought to have ‘greatly declined’ due to bycatch in fisheries (Jaaman et al. 2009), and commercial fishing (gillnetting, trawling, purse-seining) is intensive off Langkawi, Peninsular Malaysia, where bycatch of Finless Porpoises is known to occur even though it is not monitored regularly (L. Ponnampalam pers. comm. 2011). Surveys in the coastal waters of Vietnam resulted in very few sightings of cetaceans; none of the sightings were of Finless Porpoises yet local whale temples contained numerous cetacean skulls, including many from Finless Porpoises (Smith et al. 1997). The impacts of war several decades ago, compounded by intense fishing (especially the use of gillnets) in recent years and ongoing, are likely at least partly responsible for the near absence of cetaceans from these waters. In Iran (Arabian Gulf and Gulf of Oman/Sea of Oman), bycatch in fisheries appears to be the greatest threat to marine mammals and takes from apparently small, localized populations of Finless Porpoises may be unsustainable (Braulik et al. 2010). Two major marine mammal die-offs occurred in the Arabian Gulf in the 1980s and 1990s, possibly related to major oil spills (Collins et al. 2005). Even in the 1970s, Finless Porpoise sightings in Pakistani coastal waters around the Indus Delta region were apparently decreasing (Pilleri and Gihr 1972, Pilleri and Pilleri 1979) and by the 1990s the species may have virtually disappeared from this badly degraded area (see Reeves et al. 1997). The Finless Porpoise was one of several cetacean species thought to have disappeared from large parts of their previous ranges in Thailand, largely as a result of coastal habitat degradation and fisheries (IWC 1994).

Direct killing or capture of Finless Porpoises appears to be relatively rare (Reeves et al. 1997) but development of intentional fisheries for marine mammals from incidental captures (and economic benefits from subsequent consumption and marketing) may have increased in parts of Southeast Asia as preferred marine resources have been over-fished (see Perrin 2002).

The species (which presently also includes N. asiaeorientalis) is listed in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), and in Appendix II of the Convention on Migratory Species (CMS). Management measures are needed to address the threats, especially bycatch in fisheries.